This invention relates to a caster including a gas delivery means to resist backflowing and freezing of molten metal to the tip of a nozzle and an associated method.
Casters for casting molten metal, such as molten aluminum, into metal products are known. Molten metal is typically introduced into the caster from a trough that is fed from a furnace. Typically, a nozzle introduces the molten metal into the mold of the caster. In a twin belt caster, the mold is formed by a pair of opposed movable belts and a pair of opposed side dams. A metal product, such as a slab, is formed in the mold by solidifying the molten metal. An example of a twin belt caster is described in U.S. Pat. No. 4,964,456.
A recurring problem with casters utilizing a nozzle is that molten metal can freeze at the nozzle tip. This freezing of molten metal at the nozzle tip causes undesirable surface qualities in the cast slab. In addition, freezing of molten metal at the nozzle tip can cause nozzle damage.
Also, despite the known devices to seal the belt to the nozzle (see, e.g., U.S. Pat. No. 4,785,873) a space can form between the nozzle and the belt, and molten metal can enter this space, and thereafter freeze to the nozzle tip.
What is needed, therefore, is a caster that includes means for resisting freezing and backflowing of molten metal to the nozzle tip. By resisting this freezing and backflowing of molten metal to the nozzle tip, a higher quality cast metal product can be produced in the caster.